The present invention relates generally to an infrared coherent optical sensor and more particularly to a laser transceiver with modulation suitable for laser-radar applications, including use as a multifunction sensor.
Pulsed lasers and modulated lasers using various internal and external modulators are known in the art for various applications, including laser radar.
U.S. patents of interest include U.S. Pat. No. 3,573,463 to Goodwin et al., which discloses a communications system comprising a pair of laser transceivers. Each transceiver includes two laser beams of different frequencies, one of which is modulated according to an information signal. The two beams are mixed by means of a beam splitter which may be disposed either inside or outside the laser cavity. U.S. Pat. No. 3,409,369 to Bickel discloses a laser radar doppler shift system using two transmitted frequencies. Since the two frequencies are slightly different, the beat frequencies go in and out of phase, causing an amplitude modulation whose frequency is proportional to the difference in the two beat signals and the velocity of the target. U.S. Pat. No. 3,258,597 to Forrester shows a laser communication system having separate spectral line sources 10 and 11. Fried et al in U.S. Pat. No. 3,302,027 describe an interferometric arrangement for modulating light. U.S. Pat. No. 4,195,221 to Moran is directed to an optical heterodyne scanning system in which two coherent light signals are mixed to produce a different signal and Forrester et al in U.S. Pat. No. 4,391,515 show an optical transceiver with shared common optics.